Intro

Airfoils are shapes, such as wings or blades, which are used to study aerodynamic forces that are caused by passing fluids over them. Air foil research is used to help design more efficient aircraft, propellers, turbines, and many more products that require movement through fluids. this experiment a Clark Y-14 airfoil was used, which is important to note since it is not symmetrical. The aerodynamic forces felt by the airfoil are typically split into two categories, lift and drag. Lift is the component of force parallel to the airfoil, while drag is the component perpendicular to it. The values for these two parameters were found once the lift and drag coefficients were calculated from studying the pressure differentials round the airfoil. . The stall angle, the angle between the direction of airflow and the airfoil axis that causes flow separation, was also found experimentally during this lab. All of these values were then compiled and placed into a lift-drag polar to create a reference for predicting performance of an aircraft using this particular air foil.

Procedure

Before the experiment was run, the ambient pressure and temperature were recoded using the designated lab barometer and thermometer. The wind tunnel was then turned on using the power switch of the control box and slowly increased and set by the dial control. The first wind tunnel speed studied that was considered in this experiment held inclined manometer readings at 0.8 inches. Once this steady speed was reached and the angle of attack was set to -4 degrees, pressure readings from 17 pressure taps connected to the airfoil were recorded. Pressure tap readings were recorded from -4 degrees to 12 degrees, in increments of 2 degrees. Once this was completed, the stall angle was recorded. The steps for recording pressure readings were then repeated for an inclined nanometer reading of 1.2 inches. The 1.2 inclined manometer speed stall angle was recorded and the fan was then slowly turned off to end the experiment.

Equipment

This experiment used a Clark -14 Airfoil Model with 18 pressure taps connected to a multi-tube manometer. The airfoil apparatus was mounted on a rotating axis inside a subsonic draw-though wind tunnel. At one end of the tunnel, a variable speed fan draws air through the tunnel and at the other end several screens act as a filter preventing particles from entering the wind tunnel. Inside the wind tunnel in front of the air foil a pitot tube was mounted and connected to a inclined manometer. This pitot tube was used to determine the pressure on the air foil caused by the flow of air. This pressure recorded was used to calculate the free stream velocity of the air. Figure 1 below illustrates the experimental apparatus and the location of the various pieces of equipment.

Figure X: Experiment Apparatus

A. Inlet Air FlowB. Pressure Reading TapsC. AirfoilD. Pitot Probe TraverseE. Fan Speed ControllerF. Inclined Manometer for Pitot TubeG. Wind Tunnel

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